No, I mean the value 290mAh. Charger circuit doesn't need to know the capacity, it pumps up the battery till it reaches 4.2V. Percentage meter derives the capacity from voltage, there's no precise coulomb comparator (as far as I know).

There were successful attempts at total battery upgrade to 1200mAh, bumping the effective runtime to over 60 hours.

I couldn't compare the thickness because the Original one pumped itself up after I opened th sansa.

After solding I first had to bend the cables and to press hard to get the body together.Everything went well and functioned well - until I tried to put in an SDcard in. The mount is bend out of shape a little so that the snap-in Function is gone ;(

I see, so 6.2mm is perhaps too much. Thanks for the info.Another method would be sticking the battery pack onto the plastic clip. This way, with battery outside the unit, one could use batteries over 1000mAh in capacity without affecting the aesthetics too much.